Lipoplasty, or liposuction, is a well established method for removing excess fat tissue from specific locations on a patient's body, and generally involves the removal of large quantities of fatty tissue in order to treat conditions such as obesity. Autologous fat injection or transplantation, in which liposuction derived fat tissue is reinjected at a second site on the body, has become increasingly common in both cosmetic and reconstructive surgery to augment tissue or fill body and skin defects. This process is typically concerned with the removal and transfer of much smaller quantities of tissue than are involved in liposuction, often around 50-200 ml at a time.
Autologous fat injection has been used for correcting deformations and/or smoothing skin imperfections in many areas of the body, including the face, thighs, buttocks, breasts and nose. For tissue sculpting, the use of autologous fat is preferable to the use of synthetic materials such as silicone or polyacrylamide gels as it is non toxic and, not being a foreign material, is not rejected by the body.
A number of techniques for removing adipose tissue from the body are known in the art. These include pre-injection of the extraction site with hypotonic saline and hyaluronic acid, or with lidocaine and epinephrine, before removing the fatty tissue under vacuum, the removal of tissue from multiple incision sites to obtain even removal of the tissue (known as “criss-cross”), and the use of high-frequency sound waves to liquefy fat beneath the skin before removal with suction.
In order to reinject autologous fat which has been extracted from a patient, it is necessary to process the extracted fatty material to remove any excess liquid, injected solutions and other impurities. While purifying the fatty material, it is important that the extracted tissue is not damaged as this can affect the success of the graft. For example, it is believed that damaged tissue is one of the causes of injected fat being re-absorbed by the body, removing any beneficial effects which may have been obtained by the transfer.
A number of devices have been developed which seek to combine the extraction of fatty material from the body with purification and reinjection of the same material.
One such device is the LipiVage™ Fat Harvest, Wash and Transfer System, developed by Genesis Biosystems, Inc. In this system, a disposable syringe type device is attached to a low level vacuum and used to extract adipose tissue from the patient into a sterile filtration chamber. Once in the chamber, the extracted fat is mechanically filtered and washed under low pressure, the unwanted components being removed by vacuum into a waste container. The concentrated fat is then transferred into injection syringes, ready for reinjection into the patient.
Another method of autologous fat transplantation is the Coleman system, developed by Dr. S. Coleman, which combines a syringe, cannula and centrifuge. First, a solution of lidocaine, epinephrine and lactated Ringer's solution is injected into the extraction site. Adipose tissue is then removed using a syringe, purified by centrifugation, and reinserted into the patient.
The Viafill™ system is also a disposable, syringe-based system which uses a centrifuge to purify the fatty tissue, with the extraction syringe forming the chamber which is placed in the centrifuge. Reinjection can be carried out through either the harvest syringe, or through a separate transfer device.
Finally, the PureGraft™ system uses vacuum-assisted membrane filtration to remove excess fluids, blood cells and other debris from extracted adipose tissue. Following extraction of the fatty tissue from the patient, a first membrane removes loose blood cells, free lipids, fluid and other debris, and a second membrane directs the flow of the debris and aids in draining of the waste products to a waste bag. Following filtration, the extracted fat is washed with a processing solution, before being reinserted into the patient.
There are a number of disadvantages associated with the products currently available on the market. Many of them rely on centrifugation to purify the fatty tissue; although centrifugation does not generally alter the structure of the adipose tissue, it has been found that the g-forces associated with excessive centrifugation may damage and degrade the adipose tissue, resulting in an unsuccessful transfer of tissue and/or high levels of fat reabsorption by the body. In addition, the devices available are complex, often requiring transfer of the tissue from one vessel to another for purification and/or reinjection. This additional tissue handling can damage the delicate adipose tissue. It also increases the time taken to carry out the procedure, and increases the amount of equipment needed by the practitioner.